__wake_up(9)

💫 __wake_up — the Kernel API Manual, bestie edition 💫

okay so real talk, this one is a <pink>Kernel API Manual</pink> page for a function literally called __wake_up, and it is the girl who wakes up threads blocked on a waitqueue. she is small, she is powerful, she is doing the most. let's get into it 🫶

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✨ NAME ✨

__wake_up — wake up threads blocked on a waitqueue.

no cap, that's the whole job description. she wakes the sleepy ones up 💅

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🌸 SYNOPSIS 🌸

int __wake_up (struct wait_queue_head *wq_head , unsigned int mode , int
nr_exclusive , void *key );

look at her. four args, returns an int, iconic behavior only 👑

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🎀 ARGUMENTS 🎀

• wq_head — the waitqueue. this is literally the queue and bestie's whole entire world, so like, be nice to it 🦋
• mode — which threads. yes the whole vibe check of "who are we actually waking here" lives in this one argument ✨
• nr_exclusive — how many wake-one or wake-many threads to wake up. so like, are we doing a solo wake or a whole group chat situation, this arg decides 💀
• key — is directly passed to the wakeup function. not read, not verified, not questioned. just handed straight over, main character energy fr fr 🔥

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🧚 DESCRIPTION 🧚

okay so here's the actual tea.

if this function wakes up a task, it executes a full memory barrier before accessing the task state. so like, no sneaky reordering happening, the memory ordering is handled. periodt. 🌈

and she returns the number of exclusive tasks that were awaken. yep — that's a return value, that's real, that's the receipt for how many exclusive besties got the wake-up 💖

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💜 SEE ALSO 💜

kernel file ./kernel/sched/wait.c — and honestly go read it, it's giving source code chic:

• __wake_up_sync_key(9)
• __wake_up_locked_sync_key(9)
• finish_wait(9)

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⚠️ friendly reminder bestie: the return value counts the exclusive tasks that were awaken, not every task. read the number correctly or the vibe check fails 😭

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⋆｡°✩ and that's the page!! ⋆｡°✩

this masterpiece of documentation lives over in ./kernel/sched, and the version is dated October 2026 🌸 — so if you're quoting it, cite __wake_up(9) from ./kernel/sched like the academic icon you are 🎓💅 slay, bye 🦋